The invention relates to elastomeric articles used in medical applications. In particular, the invention pertains to elastomeric articles such as medical gloves having reduced coefficient of friction with respect to the skin-contacting surface.
Surfaces of elastomeric articles generally exhibit poor lubricity when contacting a dry surface, such as dry skin or other mammalian tissues, as a result of surface friction. In addition, many elastomeric surfaces display poor lubricity when contacting a damp surface as well. This is primarily due to a high coefficient of friction, or COF, of the elastomeric surface. Surfaces of elastomeric articles which exhibit a high coefficient of friction when sliding against another surface can be disadvantageous in uses where ease of donning and removal are beneficial to the use of the article. This property plays an important role in the use of medical gloves, such as examination and surgical gloves, where mechanical properties, tear resistance and tactile sensitivity during use are also beneficial features. Surgical gloves fabricated from natural rubber latex, for example, are difficult to don due to the high coefficient of friction between the glove material and the skin.
Various methods and techniques to improve the donning of gloves by reducing the coefficient of friction have been explored in the art. One such technique that has been employed is the use of talc or powders, such as calcium carbonate and starch, applied to the gloves during manufacture. Chemical methods have been explored as well to decrease the coefficient of friction of glove surface. One such method involves the halogenation of the surface of an elastomeric material to increase lubricity. However, halogenation techniques such as chlorination can adversely affect desirable mechanical properties of the material in articles such as gloves if the halogenation process is not well controlled.
A number of approaches to increase the lubricity of elastomeric articles (e.g., gloves) have been explored in the art, such as techniques using polymeric coatings, particulate micro-roughening of the surface, or combinations of both. Lubricant compositions containing silicone derivatives have been disclosed in U.S. Pat. No. 5,742,943 to Chen, which teaches flexible articles such as surgical gloves containing an elastomeric substrate layer having an elastomeric material which has been treated with a lubricant composition containing organo-modified silicone and amino-modified silicone compounds. U.S. Pat. No. 5,534,350 to Liou discloses a powder free glove containing an elastomeric layer with increased lubricity which has been treated with an aqueous dispersion of polyurethane together with a silicone emulsion. In medical applications, silicone has been widely used because of its lower surface energy, biocompatibility, e.g, high chemical and contamination resistance, and flexibility.
The use of polymeric surfaces embedded with microparticles to improve donning of gloves is known. See U.S. Pat. No. 5,792,531 to Littleton et al., for example. U.S. Pat. Nos. 5,405,666 and 5,395,666 to Brindle disclose an elastomeric glove with increased lubricity having a polymeric binding layer containing a surfactant and partially-protruding microparticles which produce a microroughening effect on the skin-contacting surface. U.S. Pat. Nos. 5,272,771 and 5,088,125 to Ansell et al. disclose an elastomeric glove with increased lubricity having a layer containing an ionic polyurethane in combination with particulate polyurethane, including acrylate or methacrylate co-polymers. U.S. Pat. No. 4,070,713 to Stockum discloses an elastomeric glove having a layer containing a binder and particulate microspheres. The binder can be composed of carboxylated styrene butadiene latex, and the particles can be composed of polyethylene, ethylenevinyl acetate co-polymers or epichlorohydrin cross-linked cornstarch.
There still exists the need for elastomeric articles such as medical gloves having improved donning properties while retaining the desirable mechanical and chemical properties associated with elastomeric articles. There is also a need in the medical community for powder-free medical gloves that avoid the disadvantages of conventional lubricity increasing techniques.
Applicants"" invention is directed to an improved elastomeric article composed of a flexible, elastomeric material and a composite coating comprising a silicone-modified polymer in combination with silicone resin particles, and to a method of making such an article. It has been discovered by applicants that the chemical interaction between silicone-based polymers and silicone resin particles can be used to produce a coating which possesses a significantly reduced coefficient of friction, thereby improving the lubricity and donning properties of the article. The interaction between the siliconized polymer and particles enhance the binding of the particles and permit very thin coating layers to be applied to articles while still maintaining surface microroughness. Articles made according to the invention exhibit extended use without significant disassociation of the particles from the coating through wear. The invention is particularly useful as applied to elastomeric articles such as medical gloves (e.g., examination and surgical gloves) where donning or skin-contacting properties with respect to both dry and damp surfaces have historically been problematic.
In particular, the invention is directed to an elastomeric article having an elastomeric material and a coating layer adhered (e.g., bonded, fused, coupled) thereto and containing a composite comprising:
a) a silicone-modified polymer; and
b) silicone particles embedded and integrated throughout said polymer;
wherein said coating layer is on a contacting surface of the article.
Elastomeric articles, such as surgical gloves, containing the coating layer and made according to the invention exhibit a topographically microroughened surface having a reduced coefficient of friction and improved lubricity and donning properties without the need for use of powders. The interaction between the components in the coating layer as well as the thickness of the coating layer and the ratio of polymer to particle collectively function to optimize the desirable properties of the article. Typically, the coating layer is applied to that surface of the article which will come into contact with skin when in use. In the case of a glove, the coating layer is on the interior surface of the glove when worn and absent from the exterior surface.
The elastomeric material used in the article can be composed of any natural or synthetic polymeric material which exhibits mechanical and chemical properties appropriate for the intended use of the article. In the case of surgical gloves, the elastomeric material must be flexible and tear-resistant with sufficient elongation and strength properties, and accommodate the tactile sensitivity requirements for gloves used in surgical procedures. Suitable elastomeric materials include, but are not limited to, those polymeric materials containing natural or synthetic rubber, polyurethane, conjugated diene homopolymers, conjugated diene co-polymers, conjugated diene and vinyl monomer copolymers, styrene block co-polymers (di-block and tri-block), and combinations thereof.
The coating layer adhered to the elastomeric material is a composite comprising a silicone-modified polymer in combination with silicone resin particles integrated and embedded therein. Any silicone-modified polymer which can adhere to the particular elastomeric material used and which can function to bind the silicone resin particles to a degree sufficient to inhibit detachment or delamination of the particles from the silicone-modified polymer, can be used. Silicone-modified polymers which can be used include those polymeric structures which can have silicone groups covalently attached to the chemical structures. Suitable silicone-modified polymers include, but are not limited to, silicone-modified polyurethanes, acrylics, vinyl, alkyl, esters, EPDM and nitriles. Preferred silicone-modified polymers are silicone-modified polyurethanes.
Homogenous or, alternatively, heterogenous mixtures of different silicone-modified polymers can be used in accordance with the invention provided they can interact with the silicone groups of the particles. Furthermore, polymers not modified with silicone groups can be present in the coating layer as well provided they do not interfere with the functionality of the silicone-modified polymers for purposes of the invention.
In general, the silicone resin particles used in accordance with the invention are those physically adapted for incorporation or integration into polymers and chemically compatible with the particular polymer used. Chemically, the silicone particles used must contain a degree of exposed silicone functional groups on the surface sufficient to chemically interact with the silicone groups bonded to the silicone-modified polymer(s) used in the composition.
The invention also includes a method of making an elastomeric article containing an elastomeric material and coating layer comprising the composite according to the invention. The method of making an elastomeric article comprises the steps of:
a) forming a first layer of elastomeric material;
b) adhering a second, friction-reducing coating layer to said first layer, said coating layer being formed from a dispersion comprising a silicone-modified polymer in combination with silicone particles integrated therein.
In a further embodiment, the coated article is subjected to a chlorination process to produce a powder-free article.
Accordingly, the silicone-modified polymer and silicone resin particle composite can be applied to elastomeric materials to decrease the coefficient of friction between the interior surface of the article and the skin of the wearer, for example. Articles such as gloves can be made by using conventional techniques in the art, which generally involve the use of a mold and the steps of dipping and curing to form layers on the mold which are subsequently removed intact.
In general, a method of making a glove according to Applicants"" invention involves the initial steps of forming a coagulant layer and elastomeric material layer onto a mold, leaching, and subsequently dipping the glove into an aqueous dispersion and curing the glove to produce a friction-reducing coating layer on the first material. Accordingly, the dispersion contains the ingredients which produce the coating layer according to the invention, i.e., the silicone-modified polymer and silicone resin particles, as well as additional ingredients well-known in the art which can be used in the dispersion which include surfactants, lubricants, releasing agents, defoamers, curing agents, pigments, plasticizers, antioxidants, and the like. After curing, the gloves are stripped from the mold, wherein the glove is inverted so as to position the coating layer on the interior surface and the uncoated elastomeric material on the exterior surface. The glove can be further subjected to a chlorination process to produce a powder-free glove.
The invention also includes an aqueous dispersion for coating elastomeric materials to increase lubricity comprising a silicone-modified polymer and silicone particles integrated therein.
Articles made according to applicants"" invention contain a contacting (e.g., skin-contacting) layer in which the silicone groups on both the silicone-modified polymer and silicone resin particles interact in a coating layer to reduce the coefficient of friction between the treated surface and the skin. Furthermore, the chemical affinity between the particles and the modified polymer enhances the binding of the particles to the coating layer and thereby reduces detachment, disassociation or delamination of the particles from the skin-contacting surface. Accordingly, one of the advantages associated with applicants"" invention is the reduced coefficient of friction and increased lubricity afforded to elastomeric articles without the use of powders. When the invention is applied to surgical gloves, for example, the gloves exhibit ease of donning while at the same time retaining the other functional features important during their use, such as strength, flexibility, and tactile sensitivity.
Another advantage of the invention is that the chemical affinity between the silicone functional groups on both the polymer and particulate components of the coating layer permits the application of a thinner coating layer while still preserving the adhesion between the particles and the layer.
Yet another advantage of the invention is that the properties of reduced coefficient of friction and increased lubricity of the coated article (e.g., glove) are substantially maintained throughout the halogenation or chlorination treatment process of the article.